why didn't harry die when Voldemort used the killing curse on him in Harry Potter and the deathly hallows

Answer: The true Master of Death is that individual who fully accepts mortality and is not afraid to die himself. It's not about possessing or using the Hallows; it's about accepting the inevitability of death, which is something Voldemort was completely unable to do, but Harry was able to accept the concept of the inevitability of death.